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java - Reading POST data from html form sent to serversocket

i try to write simplest possible server app in Java, displaying html form with textarea input, which after submitting gives me possibility to parse xml typed in that textarea. For now i build simple serversocket based server like that:

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class WebServer {

  protected void start() {
    ServerSocket s;
    String gets = "";
    System.out.println("Start on port 80");
    try {
      // create the main server socket
      s = new ServerSocket(80);
    } catch (Exception e) {
      System.out.println("Error: " + e);
      return;
    }

    System.out.println("Waiting for connection");
    for (;;) {
      try {
        // wait for a connection
        Socket remote = s.accept();
        // remote is now the connected socket
        System.out.println("Connection, sending data.");
        BufferedReader in = new BufferedReader(new InputStreamReader(
            remote.getInputStream()));
        PrintWriter out = new PrintWriter(remote.getOutputStream());

        String str = ".";

        while (!str.equals("")) {
          str = in.readLine();
          if (str.contains("GET")){
            gets = str;
            break;
          }
        }

        out.println("HTTP/1.0 200 OK");
        out.println("Content-Type: text/html");
        out.println("");
        // Send the HTML page
        String method = "get";
        out.print("<html><form method="+method+">");
        out.print("<textarea name=we></textarea></br>");
        out.print("<input type=text name=a><input type=submit></form></html>");
        out.println(gets);
        out.flush();

        remote.close();
      } catch (Exception e) {
        System.out.println("Error: " + e);
      }
    }
  }

  public static void main(String args[]) {
    WebServer ws = new WebServer();
    ws.start();
  }
}

After form (textarea with xml and one additional text input) is submitted in 'gets' String-type variable I have Urlencoded values of my variables (also displayed on the screen, it looks like that:

gets = GET /?we=%3Cnetwork+ip_addr%3D%2210.0.0.0%2F8%22+save_ip%3D%22true%22%3E%0D%0A%3Csubnet+interf_used%3D%22200%22+name%3D%22lan1%22+%2F%3E%0D%0A%3Csubnet+interf_used%3D%22254%22+name%3D%22lan2%22+%2F%3E%0D%0A%3C%2Fnetwork%3E&a=fooBar HTTP/1.1 

What can i do to change GET to POST method (if i simply change it in form and than put " if (str.contains("POST")){" it gives me string like

gets = POST / HTTP/1.1

with no variables. And after that, how i can use xml from my textarea field (called 'we')?

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1 Answer

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As there is a blank line following the headers, here is my relatively simple way of getting the post payload data, after having read the header information using the readLine() method of BufferedReader.

//socket is an instance of Socket
InputStream is = socket.getInputStream();
InputStreamReader isReader = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isReader);

//code to read and print headers
String headerLine = null;
    while((headerLine = br.readLine()).length() != 0){
        System.out.println(headerLine);
    }

//code to read the post payload data
StringBuilder payload = new StringBuilder();
        while(br.ready()){
            payload.append((char) br.read());
            }
System.out.println("Payload data is: "+payload.toString())

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